Improving Punching Shear Behavior of Glass Fiber-Reinforced Polymer Reinforced Slabs by ProQuest

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The influence of the type of reinforcement (glass fiber-reinforced polymer [GFRP] versus steel bars) on punching shear resistance was investigated. In addition, the effects of concentrating the reinforcement in the immediate column region and the influence of using steel fiber-reinforced concrete (SFRC) in the slab were also studied. The punching shear capacity, stiffness, ductility, strain distribution, and crack control were investigated. Concentrating the slab reinforcement and the use of SFRC in the slab enhanced the punching behavior of the slabs reinforced with GFRP bars. Predictions using different design guidelines are compared to the experimental results obtained from the fiber-reinforced polymer (FRP) reinforced slabs tested in this study and those tested by other researchers. Concentrating the top mat of flexural reinforcement results in beneficial effects on punching shear strength, post-cracking stiffness, and crack control. [PUBLICATION ABSTRACT]

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									 ACI STRUCTURAL JOURNAL                                                                                  TECHNICAL PAPER
Title no. 106-S40


Improving Punching Shear Behavior of Glass
Fiber-Reinforced Polymer Reinforced Slabs
by Joo-Ha Lee, Young-Soo Yoon, William D. Cook, and Denis Mitchell

The influence of the type of reinforcement (glass fiber-reinforced         1.5 times the effective flexural depth of the slab from the
polymer [GFRP] versus steel bars) on punching shear resistance             column faces for predicting the punching shear resistance.
was investigated. In addition, the effects of concentrating the               Another promising way for improving the behavior of
reinforcement in the immediate column region and the influence of          two-way slabs is the use of steel fibers in the concrete. Steel
using steel fiber-reinforced concrete (SFRC) in the slab were also
                                                                           fibers in concrete are not in contact with each other and,
studied. The punching shear capacity, stiffness, ductility, strain
distribution, and crack control were investigated. Concentrating           hence, are not as susceptible to corrosion as steel reinforcing
the slab reinforcement and the use of SFRC in the slab enhanced            bars unless they happen to be on the surface or very large
the punching behavior of the slabs reinforced with GFRP bars.              cracks develop, allowing corrosive agents to permeate into
Predictions using different design guidelines are compared to the          the concrete.4 The addition of steel fibers improves the
experimental results obtained from the fiber-reinforced polymer            toughness, impact resistance, and fatigue endurance of concrete.
(FRP) reinforced slabs tested in this study and those tested by other      Banthia et al.4 reported that the use of SFRC increased the
researchers. Concentrating the top mat of flexural reinforcement           ultimate load and toughness of slabs reinforced with FRP grids.
results in beneficial effects on punching shear strength, post-               The main objective of this study was to compare the
cracking stiffness, and crack control.                                     behavior of steel and GFRP-reinforced slab-column
                                                                           connections and investigate the effects of the banded
Keywords: fiber-reinforced polymer; punching shear; slabs; steel fibers.   distribution of flexural reinforcement and SFRC in a slab on
                                                                           the behavior of two-way slabs reinforced with GFRP bars. In
                      INTRODUCTION                                         addition, the test results were compared with the predictions
   There has been an increase in the use of fiber-reinforced               using the equations of ACI 440.1R3 and JSCE,1 developed
polymer (FRP) materials as non-corrodible reinforcement                    specifically for FRP-reinforced slabs.
for concrete structures. Only a few countries, such as Japan
(Japan Society of Civil Engineers [JSCE]1), Canada (Canadian                              RESEARCH SIGNIFICANCE
Standards Association [CSA]2), and the U.S. (American                         Generally, slabs reinforced with GFRP bars show an
Concrete Institute [ACI]3) have established guidelines for                 inferior structural behavior compared to slabs having the
the design and construction of structural concrete using FRP.              same equivalent area of reinforcement but reinforced with
The punching shear behavior of two-way slabs reinforced                    steel bars, due to the lower elastic modulus of GFRP bars. In
with FRP bars has not been fully investigated, whereas                     this research, concentrating GFRP bars in the immediate
extensive work has been performed investigating the                        column region and using SFRC in the slab near the column faces
flexural behavior of concrete members reinforced with FRP.                 improved the punching behavior. The beneficial effects of these
The punching shear behavior of an interior column                          reinforcing methods are demonstrated.
supporting a two-way concrete slab reinforced with FRP,
such as glass FRP (GFRP), carbon FRP (CFRP) or a hybrid                                  EXPERIMENTAL PROGRAM
                                                                           Details of test specimens
of glass and carbon FRP (HFRP), has been reported by                          Figure 1 shows the layout of the top and bottom slab
Banthia et al.4; Matthys and Taerwe5; El-Ghandour et al.6;                 reinforcement. The main variables were the slab reinforcement
Ospina et al.7; and Zhang et al.8 They demonstrated that                   material, the concentration of slab reinforcement around the
the differences in the mechanical properties between FRP and               column, and the presence of steel fibers in the slab concrete.
steel reinforcement (such as the relatively low modulus of                 The specimens can be divided into two series: a slab series
elasticity and the brittleness of FRP materials) affect the                reinforced with conventional steel bars (S Series) and a
slab punching behavior. There has been no research on the                  slab series reinforced with GFRP bars (GF Series). The top
effects of the concentration of FRP slab flexural reinforcement            reinforcement was distributed either uniformly or in a
around a column on the behavior. From their test results on                banded manner. The letters U and B in the specimen names
slabs containing steel reinforcing bars, Hawkins et al.,9                  indicate the layout of the slab reinforcement around the
Hawkins and Mitchell,10 Ghannoum,11 McHarg et al.,12 and                   column (U for uniform spacing of top reinforcement and B
Yoon et al.13 concluded
								
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